a display of american f-22 stealth fighter jets. a u.s. navy destroyer prepared to shoot down a north korean missile if necessary. overflights by b-2 stealth bombers and b-52s capable of carrying american nukes. an angry north korea released an animation showing the planes being shot down. in fact, if you watch north korean state tv, the country looks like it's at war. pictures of u.s. soldiers used for target practice. absolute leader kim jong un says he's put north korea's missiles at the ready calling his nuclear weapons the nation's life. secretary of defense hagel calls the north belligerent. >> it has ratcheted up the danger. >> reporter: south korea's president says she will respond to force with force. but it was calm here in seoul today. it's all bark, they say -- no

bite. >> i really don't think people are thinking they are going to come actually attack us because, you know, america has our back. >> reporter: most people in seoul think the north is bluffing. the question is why. experts say kim jong un is in the process of consolidating power and he's generating a crisis to whip his people up into a wartime patriotic frenzy so they will rally around the leader while he eliminates rivals. he's threatening war to clean house. there are big changes under way. look at this video from late 2011, the funeral of kim's father, kim jong il. the hearse surrounded by his hand-picked successors. since then nearly all have fallen from favor except kim jong un. the world's last stalinist state talking war to stay in power. pyongyang's secrecy makes the old soviet kremlin look transparent. north korea appears to want to

pick a fight. the u.s. says if it comes to that it's ready. brian? >> richard engel starting us off with what it's really like these days in seoul, south korea. richard, thanks. a stunning new assessment of national numbers came out today. it got the attention of a lot of us. it's about attention deficit, adhd and the extraordinary number of cases now being diagnosed. like one in five high school age boys in the u.s. 15% of all school age boys. 11% of all kids in our nation. these numbers show a 16% rise in cases just since 2007. all of it is leading to questions about whether adhd is being overdiagnosed and whether the medicine to treat it is being overused. our report tonight from our chief science correspondent robert bazell. >> reporter: 14-year-old ky and his 12-year-old brother kasen spend a lot of time outdoors

staying as active as possible. the boys have a tough time sitting still. both were diagnosed with adhd when they were younger. their mom karen first noticed it when the boys had trouble completing simple homework assignments. >> it was such a struggle. we only got six problems done in one hour. in between that time, he just blurted out, he says, mommy, i can't think. i just can't think. >> reporter: according to data collected by the cdc and analyzed by "the new york times," the number of children diagnosed with adhd is increasing. the times analysis shows an estimated 6.4 million, ages 4 through 17, have adhd. those numbers reflect a 50% increase in the past decade. nearly two-thirds of those children get prescriptions with amphetamine-type drugs to help treat the disorder. sales of the drugs reached $9 billion last year. >> i think this is of great concern. i think that there is some

overdiagnosis and overtreatment going on under the guise of other conditions. >> reporter: it's not just children diagnosed with adhd. on college campuses and high schools around america many students take the drugs to enhance performance on examinations. that raises many concerns. >> how is it acting on the brain in the long term? >> reporter: experts say there is no question that some children like the holmes have genuine problems that can be helped with medication. many worry there is too much diagnosis and too much medication. robert bazell, nbc news, new haven, connecticut. there is fear and anger in kaufman county, texas, after the murder of a district attorney and his wife over the weekend. mike mclelland is the second prosecutor in the area killed in as many months. this comes in the wake of the murder of colorado's prison chief last month. investigators say they are examining any and all leads. gabe gutierrez is with us from

kaufman county texas, tonight. gabe, good evening. >> reporter: brian, good evening. according to a search warrant released this afternoon, police are looking at several things including -- and they say that the d.a. and his wife were shot multiple times. they are now subpoenaing cell phone records looking for clues. so far there is no evidence to definitively link any of the murders. today under the watchful eye of armed guards employees reported for work. >> definitely concerned. >> reporter: that concern comes as a manhunt is under way for a killer. district attorney mike mclelland and his wife cynthia were found shot to death in their home saturday in what local officials call a brazen, targeted attack. federal authorities tell nbc news they are analyzing two .22 caliber shell casings found in the house. >> we are very much on alert. we have folks out to do harm to elected officials. so we take it very seriously. >> reporter: two months ago the county's assistant d.a. was gunned down outside the courthouse.

at the time mclelland had this promise for the killer of mark hasse. >> we are very confident that we are going to find you. we are going to pull you out of whatever hole you're in. we are going to bring you back and let the people prosecute you to the fullest extent of the law. >> reporter: mclelland told friends he carried a gun everywhere and was extra careful when answering his door. investigators have been working to see if hasse's shooting was connected to the killing of colorado's prison chief last month. the suspect in that case who later died in a police shootout in north texas was linked to a white supremacist group. months before, texas investigators issued a warning about the aryan brotherhood of texas planning retaliation against public officials. although federal sources tell nbc news they have yet to find a solid connection between the murders. in the meantime, texas governor rick perry is urging caution.

>> i suggest everyone should be careful about what goes on whether they are public officials or otherwise. >> reporter: and this small county outside dallas is in mourning and on edge. meanwhile, federal law enforcement officials tell nbc news they are not ruling out anything from the white supremacist group to a drug cartel to a lone gunman with a grudge. meanwhile a new interim d.a. took over the office this afternoon. brian? >> gabe gutierrez in kaufman, texas, tonight. gabe, thanks. the movie theater shooting spree in aurora, colorado, is back in the news tonight. it left 12 dead, another 58 wounded last july. prosecutors today said they will seek the death penalty for the accused gunman, james holmes. nbc's miguel almaguer covering for us tonight. miguel, good evening. >> reporter: brian, good evening. it was a dramatic and emotional day inside the courtroom where victims embraced and others wept as the prosecutor made his announcement.

james holmes had no visible reaction as the d.a. announced for james egan holmes justice is death. this after prosecutors rejected a plea deal that would have led to a guilty plea but spared holmes from the death penalty. accused of murdering 12 and injuring dozens last summer inside an aurora movie theater, holmes's lawyers will pursue an insanity plea. the victims were split. some thought the d.a. should have accepted the plea deal. others think holmes should face death for his accused crimes. brian? >> miguel almaguer covering for us from centennial, colorado, tonight. miguel, thanks. the latest from south africa is nelson mandela is improving. he spent a sixth day in the hospital and continues to respond to treatment for the lung condition. the nation and millions around the world, of course, have been in suspended animation over worry for the president. he's now been hospitalized three times in the past four months. while the white house is

cautioning nothing is final, no formal nomination has been made reports have surfaced that caroline kennedy is being vetted for u.s. ambassador to japan. just hearing that was enough to cause americans of a certain age to reflect today on a life lived largely in the public eye. our report tonight from nbc's andrea mitchell. >> reporter: the world first met her as a 3-year-old in a storybook white house. a toddler interrupting her father in the oval office. with her brother and their picture perfect parents the first family became america's symbolic ambassadors to the world. until her childhood was interrupted by tragedy, forever reminding us of heartbreak. like her mother, intensely private, caroline was still a kennedy. the question of her role became inevitable. >> has the torch been passed to caroline kennedy for future public service? >> oh, i don't -- well, i hope. i think there are many ways to serve. my uncle sets a tremendous example.

>> reporter: in 2008 at the height of the obama-clinton primary battle she jumped into the fray, comparing obama to her father. >> fortunately there is one candidate who offers the same sense of hope and inspiration. >> reporter: a new high profile. >> please welcome caroline kennedy to the podium. >> reporter: led to a brief exploration of running for the senate to replace hillary clinton. elective office not a natural fit for this kennedy. but diplomacy, her grandfather was ambassador to great britain before world war ii. her aunt jean was bill clinton's ambassador to ireland. half a century after her father's assassination with her brother, uncle and mother now gone, caroline kennedy is ready to serve, most likely in japan, a country that loves political names like former vice president walterer mondale. >> sending someone who has such high visibility, almost standing as a kind of celebrity, i think, gives her cache the minute she

lands in tokyo. >> reporter: kennedy would have to be confirmed by the senate but experts say she's a lot more qualified than many ambassadors appointed only because of the size of their campaign wallet. andrea mitchell, nbc news, washington. still ahead for us as we continue on this post easter monday night, the difficult conversation in millions of american families. and a groundbreaking new look at how to keep driving well into old age. later, a high tech line of electronics for your pets. one of the many news items floating around out there today for very good reason.

we have said this before. it's one of those bad conversations. the moment many seniors have come to dread when family members approach to take away the car keys, ending a life of driving and usually under protest. the news on this tonight is this.

researchers at m.i.t. is are researching ways to buy insurance time earlier in life to stay behind the wheel later in life. our report tonight from nbc's stephanie gosk. >> reporter: for a 72-year-old guy, stanton lyman has some good moves. the architect obsesses over two things -- his health, and his cars. what he didn't know until recently is if he keeps up the exercise he may be able to drive the cars longer and more safely. >> we know flexibility, coordination, strength, those issues are related to yielding, changing lanes, backing up which become increasingly difficult as you age. >> reporter: with funding help from the hartford insurance company m.i.t.'s age lab conducted a study of drivers 60 to 74 years old, including mr. lyman to test the theory. >> look at the speedometer please. >> reporter: for ten weeks they used video games to focus on range of motion, coordination, and strength. they were then tested in the lab using this high tech simulator

measuring reflexes, pulse rate, and eye movements. >> the study taught me to stretch and to move. and to move my body. clearly that's had an effect. >> reporter: the pretzel makes backing up easier. a little shadow boxing helps getting in and out of the car. goalie skills improve lane changes and turns. the benefits aren't just for those 65 and older. >> researchers say drivers in their 30s and 40s should start thinking about flexibility now because it can help with tricky moves like parallel parking and some of us could definitely use the help. the point is for drivers to take responsibility for the safety of their driving at an earlier age. >> driving is not about getting from point a to point b. it's about life. it's the glue that holds all those big and little things together. >> if it were taken from me i would be devastated. >> reporter: more time in the gym could be the key to more time on the road.

stephanie gosk, nbc news, cambridge, massachusetts. we are back in just a moment with the hottest tickets in town today in many towns across this country.

we are not going to show it, so it's safe to keep watching. we are going to show you one picture of kevin ware of louisville. that's him today on crutches standing up post surgery. we're happy to say he's well on his way to recovery. his injury televised live may be the one thing millions of americans will remember about easter dinner 2013. it was a horror for him obviously. his teammates, the spectators, the viewing audience, you could hear people screaming in their homes across this country. his team was powered to a dominating victory over duke.

kevin ware is expected home from the hospital tomorrow. we wish him the best. now to baseball. this was opening day. after the astros opened the season in their new league last night in houston. today featured a rare double opener in new york. both the mets and yankees played. mets won, yankees lost. both played on a beautiful spring day. not so much in minnesota. among the coldest opening days on record. 35 degrees at game time. in all this was opening day for 12 mlb teams. all the teams started with a tribute to the victims of the newtown shooting. all the teams displayed a uniform patch for the occasion. speaking of tradition, the first family and a large rabbit welcomed what seemed like half the kids in washington to their backyard today. the annual easter egg roll. there was book reading, cooking with al roker. there was the president comforting a little boy for whom it had all become just too much. on the court the president's outside shot went cold. he went 2 for 22 before moving on to the white house tennis court to hit a few instead. when we come back here

tonight, did you check the date today before work, before reading e-mails, checking the web? turns out a lot of people did not.

finally tonight, a lot of people woke up today to a new story out of france -- a sure sign of the times. it was announcing the residents of one french town would soon receive their morning newspaper by drone. the day went on from there. on the first of april though many of us try to be on guard, people are still going to try. they will see the shot and take it. a few of them are going to get through, as nbc's kevin tibbles reports for us tonight. >> reporter: mr. speaker, the president of the united states. >> it looks like you were expecting somebody else. >> reporter: yes. even the highest office in the land got into the act on a day when the pranksters come out to play. when everyone from corporations to the kid down the block tries their hand at tomfoolery. >> companies know if they do something outlandish it will be talked about. >> april fools on all of y'all. >> reporter: a makers of scope pulled a porker with bacon flavored mouthwash. >> scope bacon, for breath that sizzles.

>> reporter: honda -- >> coming soon -- >> reporter: a car that can also coif -- the honda hair. >> no hair is too tough for honda hair. isn't that nice? >> it sure is. >> reporter: want to tweet on april fools? twitter says you have to buy a vowel. five bucks a month for a, e, i, o, u. joan rivers tweets back, "twyttyr? why byy vywyls whyn yyy gyt 'y' fyr fryy? syckyrs!" beautiful ely, minnesota, banned tweeting all together today urging folks to get outdoors where only the birds tweet. mother nature's april fools joke at the ballpark. last year, 21 days over 60 degrees. this year, zero. >> reporter: how about smell searching by google nose where you can search by scent because smelling is believing. >> what does a ghost smell like? >> google nose. >> reporter: gmail today unveiled gmail blue where

everything is -- well -- >> the little lines are in blue. when you go into help it's blue. >> it's gmail, only bluer. >> reporter: and boden rolled out the man skirt but when you click to pick your size, this pops up. meanwhile, back at the white house. >> i think i'm stuck. >> reporter: kevin tibbles, nbc news, chicago. that's our broadcast on this monday night, april 1st as we start off a new week -- for real. thank you for being here with us. i'm brian williams. we hope to see you right back here tomorrow evening. we hope to see you right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com

nbc bay area news starts now. good monday evening i'm janelle wang in for jessica aguirre. >> and i'm raj mathai. in livermore a deadly accident has stalled traffic. one person is dead and another critically injured after their car drove off an embankment around 3:00 p.m. near the intersection of 580 and grant line road. all westbound lanes of 580 were closed briefly. they are now reopened but traffic is still slow through the area. new tonight at 6:00. what did they know and when? a former teacher at a well-known performing arts center is facing charges of molestation. now there are allegations that former coworkers knew what was happening but said nothing.

jodi hernandez joins us. those fellow employees might also be in legal trouble. >> reporter: it is called the mandatory reporting law and it requires people who work with or come in contact with children to report suspected abuse to police right away. tonight several employees connected to the leisure center for the arts are under the microscope and face possible criminal charges. >> it is the job of the institutions to be incredibly vigilant to protect our children. >> reporter: tonight there are questions whether those who run the center for the arts did all they could to protect children from an alleged child molester. in february prosecutors charged jason pedroza with two counts of child abuse. now there are investigations to

determine whether as many as four employees knew about the alleged abuse. >> when they know they have to report. >> reporter: legal analyst explains that by law certain employees who come in contact with children are required to report suspected abuse. the city confirms they put four people on administrative leave as they look into the matter. the d.a.'s office says it is reviewing the case and considering possible criminal charges. >> i think this d.a.'s office will bring criminal charges against at least one or more of these four people. >> reporter: parents who have had children in lesher children programs say they are outraged. >> i'm sorry. you can't just wash it under the rug. it's not something that gets washed under the rug